© 2017 Taylor & Francis. Biofunctionalizing a simple and disposable graphene oxide-modified screen-printed carbon electrode with anti-interleukin-15 antibodies has been successfully demonstrated for the first time for the label-free electrochemical detection of interleukin-15, a biomarker of early HIV infection. To improve the electrochemical reactivity and introduce carboxylic groups on the surface of screen-printed carbon electrode, high-quality graphene oxide was used for the modification of screen-printed carbon electrode. With simple modification of the screen-printed carbon electrode, the device exhibited satisfactory sensitivity, selectivity, stability, reproducibility, and regenerability. The immunosensor provided a detection limit of 3.51 ng mL −1 and a sensitivity of 0.5655 µA cm −2 mL ng −1 . The simply constructed immunosensor thus rendered promising device for immunoreactions on the surface of the electrode.